1. Field
Exemplary embodiments of the present invention relate to a temperature sensing circuit.
2. Description of the Related Art
A temperature sensing circuit for sensing a temperature change is one of very important circuits in an integrated circuit. For example, the temperature sensing circuit plays a very important role in a circuit for protecting a circuit at a high temperature, a circuit having operation properties varying at a predetermined temperature, and a circuit such as a thermometer. The operation speed, an internal resistance value, and the like of the integrated circuit change in response to temperature. Specifically, as the degree of integration of the integrated circuit is increased, it is more important to accurately sense a temperature change because the temperature change has a significant influence on operation processes of the integrated circuit.
FIG. 1 is a configuration diagram of a conventional temperature sensing circuit.
Referring to FIG. 1, the temperature sensing circuit includes a comparison signal generation unit 110, a control unit 120, and a change detection unit 130.
The operation of the temperature sensing circuit will be described with reference to FIG. 1 below.
The comparison signal generation unit 110 includes a plurality of delay units (not illustrated in FIG. 1) and generates a comparison signal R0. The change detection unit 130 measures the amount of temperature change using the difference between pulse widths of the comparison signal R0 and a reference signal RE. The pulse width of the comparison signal R0 corresponds to the sum of delay values of activated delay units among the plurality of delay units. The delay units are activated or deactivated in response to control codes CON<0:A> generated by the control unit 120.
In order to accurately measure the temperature change, it is desirable to perform an operation for adjusting the pulse widths of the comparison signal R0 and the reference signal RE to be substantially equal to each other at an initial temperature before a temperature sensing operation. Since the delay units may have different delay values depending on fabrication processes, if the number of the delay units activated at the initial temperature is fixed, the pulse width of the comparison signal R0 changes depending on the fabrication processes.
In this regard, in order to compensate for a change in the delay values of the delay units depending on the fabrication processes, the control unit 120 adjusts the number of the delay units to be activated until the pulse widths of the comparison signal R0 and the reference signal RE are substantially equal to each other at the initial temperature. Such an operation will be called a calibration operation.
For example, when the pulse width of the comparison signal R0 is larger than the pulse width of the reference signal RE, the control unit 120 reduces the number of the activated delay units. In an opposite case, the control unit 120 increases the number of the delay units to be activated. If the pulse widths of the comparison signal R0 and the reference signal RE are substantially equal to each other, the control unit 120 substantially maintains the number of the activated delay units.
After the calibration operation is completed, the change detection unit 130 counts a clock CLK when the pulse widths of the comparison signal R0 and the reference signal RE are different from each other. The number of countings of the clock CLK, more accurately, the time difference between the pulse widths of the comparison signal R0 and the reference signal RE is proportional to the amount of the temperature change.
In order to sense the temperature change more accurately, the comparison signal generation unit 110 may include and activate a large number of delay units. That is, when the number of delay units is large, since the sum of delay values of activated delay units significantly changes even with a slight temperature change, it is easy to measure the time difference between the pulse widths of the signals. However, the number of the delay units is increased, resulting in an increase in a circuit area. Therefore, in order to substantially increase the sensitivity of the temperature sensing circuit, the circuit area may be increased.
Since details are disclosed in “Dual-DLL-based CMOS all-digital temperature sensor for microprocessor thermal monitoring, IEEE international solid-state circuit conference, pp. 68-70, 2009”, detailed description thereof will be omitted.